Preparation of diester oil solutions of mineral oil-free basic alkaline earth metal mahogany sulfonates



iinited States Tatent 2,994,661 PREPARATION OF DIESTER OIL SOLUTIONS OFMINERAL OIL-FREE BASIC ALKALINE EARTH FVIETAL MAHOGANY SULFONATES Lee V.Brown, Chicago, 111., assignor to Sinclair Refining Company, New York,N.Y., a corporation of Maine No Drawing. Filed Apr. 9, 1958, Ser. No.727,250 4 Claims. (Cl. 252-33) This invention relates to a process forthe manufacture of an additive solution. More particularly, my inventionpertains to a process for the manufacture of an additive concentrate ina diester synthetic lubricant vehicle.

Previous work with diester base synthetic lubricants has shown thatmineral lubricating oil can be incompatible with diesters of lubricatingviscosity. Thus the use of conventional mineral lubricating oil dilutedadditives in the diester base liquids requires that the additives bedeoiled. Investigations with diester base lubricants using deoiledconventional additives established that the method of compounding is anelement of prime importance particularly when incorporating additiveswhich have constituents reactive with the diester lubricant base. Forinstance, additives frequently employed in the diester lubricants arebase oil-soluble, basic mahogany sulfonates of the alkaline earth metalsespecially those of calcium and barium. In designating these sulfonatesas basic I refer to the fact that the alkaline earth metal is present inan amount in excess of that theoretically required to react with thesulfonic acid from which it was made, for instance, at least about 1.2equivalents. In the case of the barium sulfonates there is usually atleast about 1.5 equivalents of barium in the sulfonate and usually thebasic sulfonates do not have more-than about 5 equivalents of alkalineearth metal.

Mineral oil-free basic alkaline earth metal mahogany sulfonates can bedissolved directly in a diester vehicle only after prolonged agitationand heating. The use of a volatile solvent such as benzene to firstdissolve the sulfonate followed by mixing with the diester and toppingto remove the benzene solvent, results in saponification of the diesterand subsequent gelation of the mixture.

The purpose of this invention is to overcome these dificulties byproviding a method for incorporating mineral lubricating oil-free, basicalkaline earth metal mahogany sulfonates into diester syntheticlubricants. Further this invention provides a method of producing aconcentrate of a mineral oil-free, basic alkaline earth metal mahoganysulfonate in a diester synthetic lubricant vehicle where the sulfonateis, for example, about 25 to 75% of the composition. This concentrate iscompatible with synthetic diesters of lubricating viscosity and thesulfonate does not deleteriously react with the diester of theconcentrate or a diester lubricant base oil to which it is added. Theseconcentrates are clear, stable and easily pumpable to facilitatehandling, storage and blending into synthetic lubricants of the diestertype.

This invention consists essentially of dissolving in a volatile liquidhydrocarbon solvent a mineral oil-free mahogany sulfonate, for instanceformed by the process of reacting an oil-soluble sulfonic acid petroleumoil with ammonia, an alkali metal such as sodium, lithium or potassium,or an alkaline earth metal such as calcium or barium; and extracting theresulting sulfonate as with alcohol, say of 1 to 3 carbon atoms, andwater. The ammonium and alkaline metal sulfonates are soluble in a 50volume percent solution of isopropanol in water. The liquid hydrocarbonsolvent is compatible with diester oils of lubricating viscosity andboils primarily below about 350 F., preferably below about 300 F. Thesolvent usually contains a large proportion of aromatic conicestituents. The resulting solution is reacted with an excess of a basicinorganic compound of an alkaline earth metal such as the oxides,hydroxides and carbonates, to produce the corresponding minerallubricating oil-free, basic alkaline earth metal mahogany sulfonate suchas that of barium. The oil-free basic alkaline earth metal mahoganysulfonate is carbonated by contact with carbon dioxide while obtaining apH of not more than about 8.5 by carbonation. The diester syntheticlubricant vehicle, formed from alcohols and polycarboxylic acids, isthen added. The resulting product is distilled to remove the solvent andrecover the additive concentrate.

in my process the oil-free mahogany sulfonate (which can be derived fromconventional oleum or sulfur trioxide treatment of mineral oildistillates) is dissolved in a volatile hydrocarbon solvent such astoluene, aromatic naphtha or heptane with generally a solvent tosulfonate ratio range of about 1:1 to 5:1 or more. The preferred solventto sulfonate range in my invention is about 1.25 to 30:1. The resultingsolution is reacted with an excess of a basic inorganic compound of analkaline earth metal to produce the corresponding basic alkaline earthmetal mahogany sulfonate. The mineral lubricating oilfree alkaline earthmetal mahogany sulfonate is then carbonated, for instance in atemperature range of about 70 F. to 220 F. The preferred temperaturerange of carbonation is about F. to 150 F. The preferred pressure rangefor the absorption of carbon dioxide which is aided by higher pressureswould be from about atmospheric pressure to about 10 atmospherespressure. During carbonation a pressure range from about atmosphericpressure to about 70 atmospheres can successfully be employed. Thesolution is carbonated to give a maximum pH of about 8.5. The preferredpH range for my invention is about 7.5 to 8.5. The diester vehicle isthen added to my carbonated solution. The diester vehicle of lubricatingviscosity is formed from alcohols and polycarboxylic acids. Among thedicarboxylic acids employed are those having from 2 to 12 carbon atomssuch as adipic, azelaic, suberic, alkenyl succinic and sebacic acids.The alcohols employed usually contain 4 to 20 carbon atoms such asbutyl, hexyl and Z-ethylhexyl and dodecyl alcohols; preferably thealcohol contains 6 to 12 carbon atoms. The resulting solvent can bedistilled by the conventional methods of either batch or continuousdistillation. Topping can be accomplished at reduced pressures to removethe last trace of volatile solvent. During distillation the solutionshould not exceed a maximum temperature of about 350 F., preferably notabove about 300 F.

The following example will serve to illustrate my invention but it isnot to be considered limiting.

Example.777 pounds of sulfonic acid oil is produced by the treatment ofa 150 lb. oleum/bbl. of dewaxed Mid-Continent 250 SSU/ 100 F.lubricating oil distillate. The acid oil is charged in an agitator andneutralized with 14.1 lbs. of ammonium hydroxide, 56.4 lbs. of water and67.3 lbs. of 99 percent isopropyl alcohol are added to the agitator atF. and then two hours settling time is allowed. The lower alcohol layeris withdrawn. Then 6,000 grams of the alcohol extract is diluted with 50percent isopropyl alcohol-water solution to a total volume of 8 gallons.The alcohol solution is extracted six times with 4,000 cc. charges ofhexane which are discarded and the remaining isopropyl alcohol is toppedoil at about 208 F. The sulfonate-Water residue from the alcoholrecovery step is mixed with about 2 gallons of toluene and neutralizedwith 1,080 grams of barium oxide (300 percent of theoretical). Theremaining Water is topped off and the toluene solution is filtered. Thesolution is then distilled and the toluene removed with a resultingrecovery of about 5 lbs. of mineral oil-free solid basic bariumsulionate. Analysis of the basic barium sulfonate discloses:

Percent barium 22.2 Base No. to pH -4 78.1 Next 1513 grams of oil-freebarium sulfonate is dissolved in 2323 grams of toluene and carbonated atatmospheric pressure with carbon dioxide gas at about 100 F. until .a pHof 8.4 is obtained. Then 1513 grams of di-2-ethylhexyl sebacate (Plexol201) is added to the toluene solution and the toluene is distilled ofiat atmospheric pressure and the material is topped at 300 F. and mm. Hg.The product is a clear dark liquid Without evidence of insolubles suchas gels.

The following example Will serve to illustrate a conventional processfor manufacture of an additive concentrate in a synthetic diesterlubricant vehicle.

Example.-20,024 grams of oil-free ammonium mahogany sulfonate are mixedwith 8 gallons of toluene and 1 gallon of water. The resulting solutionis contacted with 2450 grams of barium oxide (300 percent oftheoretical), and then dehydrated and filtered. Suflicient of thetoluene solution is then added to 3632 grams of di- 2ethylhexyl sebacateto give a composition containing 3632 grams of the oil-free basic bariumsulfonate. The temperature is then raised to facilitate the topping oil?of toluene. As the solution reaches a temperature of about 240 F., wellbelow required temperature for toluene topping, an insoluble gel isformed. This gel is essentially a barium salt of sebacic acid and freealcohol.

The product of my invention is a clear dark liquid .which has noevidence of gelation and is essentially void of insolubles While thecommercial process example exhibited high viscosity and saponificationof the diester and then subsequent gelation of the mixture.

I claim:

1. A method of producing a solution of mineral oilfree basic alkalineearth metal mahogany sulfonate in a diester lubricant vehicle whichconsists essentially of reacting a mineral lubricating oil-free mahoganysulfonate dissolved in a volatile hydrocarbon solvent boiling belowabout 350 F., with a basic inorganic alkaline earth metal compound toproduce a basic alkaline earth metal mahogany sulfonate solution,carbonating the solution to a pH of not more than about 8.5, adding tothe carbonated solution a diester vehicle of lubricating viscosityformed from alcohol having 4 to 20 carbon atoms and dicarboxylic acid of2 to 12 carbon atoms, and distilling the resulting solution to removethe solvent.

2. The method of claim 1 in which the alkaline earth metal is barium.

3. The method of claim 1 in which the diester lubricant vehicle isdi-Z-ethylhexyl sebacate.

4. A method of producing a solution of mineral oilfree basic bariummahogany sulfonate in a diester lubricant vehicle which consistsessentially of reacting a mineral lubricating oil-free ammonium mahoganysulfonate dissolved in toluene, with an oxide of barium to produce abasic barium mahogany sulfonate solution, carbonating the solution to apH of not more than about 8.5, adding di-Z-ethylhexyl sebacate to thecarbonated solution, and distilling the resulting solution to remove thesolvent.

References Cited in the file of this patent UNITED STATES PATENTS2,723,236 Assefi et al. Nov. 8, 1955 2,861,951 Carlyle Nov. 25, 1958 VFOREIGN PATENTS 786,167 Great Britain Nov. 13, 1957 787,459 GreatBritain Dec. 11, 1957 OTHER REFERENCES I. and E. Chem, vol. 46, No. 5,May 1954, pages 1035-1042.

1. A METHOD OF PRODUCING A SOLUTION OF MINERAL OILFREE BASIC ALKALINEEARTH METAL MAHOGANY SULFONATE IN A DIESTER LUBRICANT VEHICLE WHICHCONSISTS ESSENTIALLY OF REACTING A MINERAL LUBRICATING OIL-FREE MAHOGANYSULFONATE DISSOLVED IN A VOLATILE HYDROCARBON SOLVENT BOILING BELOWABOUT 350*F., WITH A BASIC INORGANIC ALKALINE EARTH METAL COMPOUND TOPRODUCE A BASIC ALKALINE EARTH METAL MAHOGANY SULFONATE SOLUTION,CARBONATING THE SOLUTION TO A PH OF NOT MORE THAN ABOUT 8.5, ADDING TOTHE CARBONATED SOLUTION A DIESTER VEHICLE OF LUBRICATING VISCOSITYFORMED FROM ALCOHOL HAVING 4 TO 20 CARBON ATOMS AND DICARBOXYLIC ACID OF2 TO 12 CARBON ATOMS, AND DISTILLING THE RESULTING SOLUTION TO REMOVETHE SOLVENT.